Area Forecast Discussion
Issued by NWS Bismarck, ND

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FXUS63 KBIS 212238
AFDBIS

Area Forecast Discussion
National Weather Service Bismarck ND
438 PM CST Tue Feb 21 2017

.UPDATE...
Issued at 429 PM CST Tue Feb 21 2017

Added a chance of thunderstorms to southwest North Dakota for late
this afternoon and early evening per observed upstream trends
across southeast Montana through 2230 UTC. A modestly unstable
airmass with around 250-500 j/kg of MUCAPE across southeast
Montana into southwest North Dakota near a stationary front is
expected to remain through the early evening, with multiple
impulses to help sustain convection ahead of the main upper level
shortwave across central Montana. Cannot rule out some small hail
with a cool atmospheric column.

&&

.SHORT TERM...(This evening through Wednesday)
Issued at 305 PM CST Tue Feb 21 2017

Main forecast issue in the short term period will be precipitation
chances/types/amounts.

Both the global and mesoscale models are a little more robust
today with their qpf associated with a quick moving low pressure
system tracking across the Dakotas tonight into Wednesday.

Currently, radar reflectivities continue to increase across
western and central ND in the left exit region of a 130 kt upper
jet pushing across the Rockies and into the northern plains.
Current surface analysis is a little south of the NAM/GFS with the
surface low, but the simulated radar matches pretty well with
current radar. We do see some convection over southeast Montana.
Will need to monitor, but think that by the time it reaches ND the
CAPE will be limited.

Mesoscale models track precipitation across mainly along and
north of Highway 200 this evening with a possible maxima along a
line from Williston/Watford City eat to Bottineau Rugby. Mesoscale
models do look to be too quick to develop snow, considering our
current warm temperatures (although the far northern tier counties
still remain much colder than most of the area). Global models
also seem to pick up on a more convective/banded precipitation
element. Unfortunately, although a same general area is depicted,
the exact track any heavier band varies from model to model. We
opted to utilize a blend of global and mesoscale models with our
previous forecast to get a general qpf forecast, this is quite a
bit higher than our previous forecast, but muted from some of the
possible model solutions.

A look at the global solutions does show some good FG forcing with
strong lapse rates this evening, but with weak synoptic scale
forcing. In addition, precipitation should remain liquid for most
of the evening. Late tonight, synoptic scale forcing increases but
the best FG forcing shifts northeast of the forecast area, but
there could be a few hours tonight where the various forcing
elements match up. Given our model blend of snow ratio`s and our
blended solution of QPF, we ended up with an area of 1 to 2 inches
of snow from basically Highway 2 to Interstate 94. Could be a
band of higher snow amounts within the main area, from around
Watford City and Williston through New Town and Minot to Rugby.

It looks like a pretty quick transition from rain to snow as
colder air drops south tonight, especially north. However we will
still carry a band of mixed precipitation as we transition from
rain to snow.

On Wednesday we lose our cloud layer aloft across the north so
there is a small potential of freezing rain. But think that by the
time we see this occur, our precipitation chances will have moved
farther south. In the south, after the transition from rain to
snow late tonight or early Wednesday, we will likely see
precipitation shift back to rain, or a rain/snow mix as we warm up
during the day, then finally change back over to snow for good
early Wednesday evening.

We will issue a SPS highlight the return to colder weather, 1 to 3
inches of snow and a period of mixed precipitation.

.LONG TERM...(Wednesday night through Tuesday)
Issued at 305 PM CST Tue Feb 21 2017

Cold air returns for good by Wednesday night. Thursday through
early next week will see temperatures return to near normal with
highs in the 20s to low 30s and morning lows in the high single
digits to teens. We will see a clipper or two bring small
precipitation chances, but the main storm track will remain well
to our south through the extended period.

&&

.AVIATION...(For the 00Z TAFS through 00Z Wednesday evening)
Issued at 429 PM CST Tue Feb 21 2017

Generally VFR conditions are forecast this afternoon, with gradually
lowering ceilings from north to south beginning this evening. Rain
showers are possible west and north at KDIK and KISN, and later
this afternoon at KMOT. Scattered thunderstorms are also possible
across southwest North Dakota late this afternoon and early
evening. Expect deteriorating conditions tonight from north to
south as a large area of MVFR and IFR ceilings spreads southward
across the area after 03 UTC, with a mix of rain and snow at
first, then becoming all snow later tonight.

&&

.BIS WATCHES/WARNINGS/ADVISORIES...
NONE.
&&

$$

UPDATE...AYD
SHORT TERM...twh
LONG TERM...twh
AVIATION...AYD



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